Answer:
Oliver and Peter both uses same length string.
Step-by-step explanation:
Suppose length of rope or string = x meters
Oliver divide his rope into four equal parts

Each part length is

NOw Oliver used 3 part of the string out of four parts
that means total used string is 3/4
Now peter also have same length of string = x meter
He divides the string eight equal parts and use the 6 parts out of 8
each part length is :

Use 6x/8
simplify the fraction 6x/8
divide by 2 both numerator and denominator
6x/8 = 3x / 4
So both uses same part of string.